Compressor

ABSTRACT

A small multistage nonlubricated compressor for air and other gases has annular concentric low-lift inlet and discharge reed valves. At least the discharge valve is backed by a backing member that has the curvature of the open discharge valve. Each cylinder has a set of interchangeable liners each of which has inlet openings through the side walls thereof, and the inlet openings of each liner of a set are spaced different distances along the axis of the liner from the openings of the other liners of the set. Selection of an appropriate liner thus predetermines the cylinder capacity without upsetting the dynamic balance of the compressor.

United States Patent [191 Paget 1 COMPRESSOR [76] Inventor: Win W.Paget, 2044 Lancaster Rd,

Homewood, Ala. 35209 [22] Filed: May 3, 1972 [21] Appl. No.: 249,914

[451 Apr. 30, 1974 Primary Examiner-William L. Freeh Attorney, Agent, orFirm-Young & Thompson 5 7 ABSTRACT A small multistage nonlubricatedcompressor for air and other gases has annular concentric low-lift inletand discharge reed valves. At least the discharge valve is backed by abacking member that has the curvature of the open discharge valve. Eachcylinder has a set of interchangeable liners each of which has inletopenings through the side walls thereof, and the inlet openings of eachliner of a set are spaced different distances along the axis of theliner from the openings of the other liners of the set. Selection of anappropriate liner thus predetermines the cylinder capacity withoutupsetting the dynamic'balance of the compressor.

14 Claims, 17 Drawing Figures [52] US. Cl 417/564, 137/525.3 [51] t.F04b 21/02 [58] Field of Search a; 417/534, 454, 564

[56] References Cited UNITED STATES PATENTS 3,403,847 10/1968 Parker .1417/454 2,935,248 5/1960 Gerteis 417/564 3,070,122 12/1962 Weatherheadet a1... 417/564 3,066,856 12/1962 Frank 417/564 2,213,256 9/1940 Paget417/562 1,996,763 4/1935 Halleck 417/564 m I 1 I i 26 2B I5 PATENTEDAPR30 m4 SHEET 1 OF 3 COMPRESSOR The present invention relates tocompressors, more particularly of the small multistage nonlubricatedtype for compressing air and other gases.

It is known to provide concentric valving in compressors, in whichannular flat valves require only a relatively low lift and a lowclearance volume while providing comparatively large valve areas.However, the guidance of such valves is difficult because of frictionproblems and resulting wear on the valves and/or their guides.

Accordingly, it is an object of the present invention to providecompressors with substantially annular inlet and discharge valves, whichoperate substantially frictionlessly and with very little wear.

Another object of the present invention is the provision of compressorswith annular valves that can operate at very high speed with relativelylow inertia.

It is also known to provide compressors with means for varying thecapacity of the cylinder. In single-stage compressors, a common meansfor doing this is to use eccentrics of various throws, in combinationwith means for adjusting the cylinder assemblies axially for the purposeof maintaining minimum end clearance. However, it is particularlyadvantageous to provide some means for varying cylinder capacity in thecase of two-stage compressors, as small nonlubricated compressors arerequired at a wide range of capacities and discharge pressures. When itis attempted to change the capacity of a cylinder of a multicylindercompressor by changing the throw, the dynamic balance is disturbed; andthis is particularly disadvantageous in the case of high-speedcompressors.

Accordingly, it is an object of the present invention to provide meansfor changing the capacity of a compressor cylinder without upsetting thedynamic balance thereof.

Still another object of the present invention is the provision of meansfor increasing the capacity of a compressor cylinder without enlargingthe same.

Finally, it is an object of the present invention to provide compressorswhich will be relatively simple and inexpensive to manufacture, easy toassemble, adjust, operate, maintain and repair, and rugged and durablein use.

Other objects, features and advantages of the present invention willbecome apparent from a consideration of the following description, takenin connection with the accompanying drawings, in which:

FIG. 1 is a longitudinalsectional view ofa compressor according to theinvention;

FIG. 2 is an' elevational view of the inner side of a compressor head;

FIG. 3 is a cross-sectional view taken on the line 33 of FIG. 2;

FIG. 4 is an elevational view of the discharge valve seat;

FIG. 5 is an axial view of the inlet valve stop plate, as seen from theleft of FIG. 1;

FIG. 6 is an elevational view of the inlet valve seat;

FIG. 7 is an elevational view of a first embodiment of inlet valve;

FIG. 8 is an edge view of the inlet valve of FIG. 7;

FIG. 9 is an elevational view ofa second embodiment of inlet valve;

FIG. 10 is an elevational view of the discharge valve;

FIG. 11 is an edge view of the discharge valve;

FIG. 12 is an elevational view of the discharge valve backing member;

FIG. 13 is a cross-sectional edge view of the discharge valve backingmember;

FIG. 14 is a fragmentary view of the left end of FIG. 1, showing amodification in which the inlet and outlet valve seats are made integralwith each other;

FIG. 15 is a view similar to the left end of FIG. 1, but showing anothermodified construction;

FIG. 16 is an elevational view of an inlet valve for use with the FIG.15 embodiment; and

FIG. 17 is an elevational view of a discharge valve for use with theFIG. 15 embodiment.

Referring now to the drawings in greater detail, and first to FIG. 1,there is shown a two-stage compressor according to the present inventioncomprising an open crankcase 1 which supports a drive shaft 2 inbearings 3. Conventional drive means (not shown) are provided forrotating shaft 2. Diametrically opposed eccentrics 4 and 5 are keyed toshaft 2 to be driven thereby and are connected by bearings to the innerends of connecting rods 6 and 7 which in turn drive pistons 8 and 9 ofthe two compressor stages.

Low pressure cylinder 10 has an inlet 11 and a discharge 12 and agenerally cylindrical cylinder liner 13. High pressure cylinder 14 hasan inlet 15 and a discharge 16 and a generally cylindrical liner 17.Discharge 12 is connected to inlet 15 by finned tubing (not shown).

In addition to the annular inlet and discharge valves to be describedhereinafter, each cylinder liner 13 or 17 has an annular series ofopenings 18 or 19 through the side wall thereof, the openings 18communicating with inlet 11 and the openings 19 communicating with inlet15. All ofthe openings of a given liner are at the same location alongthe axis of the liner. However, for each cylinder, there is a setconsisting of a plurality of liners that are identical to each otherexcept for the location of the openings, the openings of each liner ofthe set being at a different axial location from the openings of theother liners of the set.

As the liners 13 or 17 of each set would differ from each other inappearance only by the axial location of the openings 18 or 19, it isnot believed to be necessary to show in the drawing more than one linerof each set.

The liners 13 and 17 need not function both in the same way. Toillustrate this point, the liner 13 has been shown as a liner whichincreases the capacity of its associated cylinder without enlarging thesame; while the liner 17 decreases the capacity of its cylinder.Specifically, when the piston 9 is at the bottom of its stroke, the lip20 of piston 9 will only partially expose the openings 18. The intakemovement creates an underpressure in cylinder 10, due to the resistanceto air flow of the inlet valves and passages; but when the openings 18are exposed, this underpressure is quickly relieved by a flow of air inthrough the openings 18. Upon the return or compression stroke, however,the lip 20 of piston 9 will seal the openings 18 before the pressure canrise to expel through openings 18 the same amount of air that enteredthrough openings 18. In other words, the amount of air compressed incylinder 10 per stroke will be greater because of openings 18 than if noopenings 18 were provided; and the capacity of cylinder -is thusincreased for a given stroke or throw of piston 9, without an actualenlargement of the cylinder.

The liner 17 is shown as an example of an arrange ment in which thecylinder capacity is selectively decreased. At the bottom ofits stroke,the lip 21 of piston 8 is a substantial distance below the openings 19,so that the capacity of cylinder 14 is correspondingly reduced by theoutflow of air through openings 19 during the first portion of thecompression stroke, without the need for changing the length of thatstroke. It is to be noted, in connection with high-pressure cylinder 14'and the openings 19 of its liner 17, that, in addition to theconventional piston ring 22 at the lip 21 of piston 8, a rearwardlyspaced ring 23 is also provided to prevent leakage back along the pistonafter ring 22 has passed the openings 19 during the compression stroke.A corresponding second piston ring is not needed in the low-pressurestage.

The liners l3 and 17 may be made of any suitable self-lubricatingmaterial such as graphite, polyimide, polytetrafluoroethylene, etc. Theouter surfaces of the pistons in sliding contact therewith may behardchrome plated in the case of graphite liners or may be of aluminumwith a hard anodized peripheral surface if the liners are of polyimideor polytetrafluoroethylene.

Air to be compressed in each stage is drawn in through an annular inletvalve and discharged through an annular discharge valve, the inlet anddischarge valves being concentric and of the flexible or reed type. Thevalves of the high-pressure stage will be described hereinafter, itbeing understood that those of the lowpressure stage'can have the samegeneral configuration if not the same dimensions. v

The left end of the compressor as shown in FIG. 1 is closed by acylinder head 24 which is best seen in FIGS. 2 and 3 as comprising aperipheral flange 25 that borders inlet and discharge passageways 26 and27, respectively, and that clamps the outlet valve seat 28 (FIG. 4)between itself and the casing 1 when head 24 is secured to casing l byconventional bolts (notshown). Head 24 has a central hollow boss 29 inwhich is received the screw-threaded shank 30 of the inlet valve stopplate 31 (FIG. 5 A nut 32 retains stop plate 31 in the FIG. 1 position,with inlet valve seat 33 (FIG. 6) clamped between plate 31 and boss 29.Inlet valve seat 33 has an annular series of inlet openings 34therethrough and disposed thereabout.

In FIGS. 7 and 8 is shown an inlet valve 35 for use in the compressor ofFIG. 1, comprising a very thin annular wafer of stainless steel or thelike, having a pair of diametrically opposed tabs 36 integral therewithon its inner periphery, and a similar pair' of diametrically opposedtabs 37 on its inner periphery at 90 to the tabs 36.

Inlet valve stop plate 31 has a pair of diametrically opposed relativelyshallow recesses 38 therein which receive tabs 36 of valve 35 withminimum clearance. Thus plate 31 in effect pinions valve 35 to the underside of inlet valve seat 33 on a line passing through tabs 36.

Plate 31 has relatively deeper recesses 39 therein, that arediametrically opposed to each other and at 90 to recesses 38; and thetabs 37 are free to ride in recesses 39.-The depth of recesses 39 thuslimits the lift of valve 35 when valve 35 opens by bending about theimaginary line passing through tabs 36. Thus tabs 36 are retainer tabsfor securing valve 35 to its seat, while tabs 37 limit the lift of valve35 when they strike the bottoms of recesses 39. Upon the intake strokeof the piston, air to be compressed is drawn on through inlet passageway26 through openings 34 and past the flexed valve 35 into the cylinderchamber; while upon the compression stroke of the piston, valve 35 isforced against seat 33 and the openings 34 are thus all closed.

An alternative form of inlet valve 40 is shown in FIG. 9, which is athin flat wafer of stainless steel or the like. as in the embodiment ofFIGS. 7 and 8, but which is not centrally open. Instead, valve 40 haslift-limiting tabs 41 which perform the same function as the tabs 37 inFIG. 7; but the internal portion of valve 40 is delimited by twoW-shaped slots 42 which are connected to the outer periphery of valve 40by bridges 43 that serve to fasten the peripheral or flexing portion ofvalve 40 to the central or secured portion of valve 40. Needless to say,when the valve of FIG. 9 is used, it is not necessary to provide plate31 with recesses 38.

An outlet valve 45 suitable for use with the compressor of FIG. 1 isshown in FIGS. 10 and 1], which may also be a thin flat annular wafer ofstainless steel or the like. Valve 45 has retention tabs 46diametrically opposed on its inner periphery, which are secured withminimum clearance in recesses 47 on an annular boss 48 of cylinder head24. Boss 48 backs up inlet valve seat 33 radially outwardly of openings34; and by receiving tabs 46 in recesses 47, boss 48 secures dischargevalve 45 against seat 33 along an imaginary line passing through tabs 46with the outer periphery of outlet valve 45 overlying the innerperiphery 49 of discharge valve seat 28. The discharge outlet of thecylinder is thus the annular space between the outer periphery of inletvalve seat 33 and the inner periphery 49 of v discharge valve seat 28.

A discharge valve backing member 50 is provided, as shown in FIGS. 12and-13, which is of spring steel and is generally annular in shape andis substantially thicker than valve 45. Backing member 50 has a naturalcurvature in its unstressed condition as shown in FIG. 13 and hasdiametrically opposed tabs 51 on its inner periphery. Tabs'5l, like thetabs 46 on valve 45, are also received in the recesses 47 on boss 48 ofcylinder head 24, so that boss 48 holds discharge valve 45 and its.

backing member 50 in sandwich relationship with the backing member 50normally curving away from valve 45 about a bend line that passesthrough tabs 51. Boss 48 has lugs 52 thereon, as seen in FIGS. 2 and 3,lugs 52 pressing on those portions of backing member 50 which are shownat the extreme left and right of FIG. 13, thereby to flatten backingmember 50 only somewhat from its unstressed condition as shown in FIG.13 and to urge member 50 against valve 45 at least along the imaginaryline passing through tabs 51. Backing member 50 is of course on the sideof valve 45 which is opposite the piston.

Upon the intake stroke of the piston, valve 45 will be drawn flatagainst the adjacent portions of seats 28 and 33 and will close theannular discharge opening. But upon the compression stroke of thepiston, the air leaving the cylinder will flex valve 45 about the bendline passing through tabs 46, and valve 45 will progressively spread outagainst backing member 50. Valve 45, like valve 35, thus operatesfrictionlessly and without substantial wear. Indeed, the cushion of airtrapped between valve 45 and backing member 50 ensures that even at thehighest speeds, valve 45 will not be subjected to damage.

One might wonder why valve 45 needs a backing member 50 but inlet valve35 does not. The answer is that the inlet valve opens slightly after thepiston passes top dead center and closes slightly after bottom deadcenter. In both of these positions, the piston is traveling slowly andthe pressure differential across the valve is relatively small.

By contrast, the discharge valve 45 opens when the piston is at aboutmidstroke, at about the fastest point in the travel of the piston. Therate of pressure change in the cylinder at this point is almostunbelievably rapid. In certain high-speed high-pressure compressors ofthe general type of the invention, the rate of pressure change at thispoint can be over 2 million pounds per square inch per second. Even avery light discharge valve with very low lift will still have enoughinertia to cause the instantaneous pressure in the cylinder to exceedthe discharge pressure by at least percent. This overpressure literallytires the discharge valve off its seat, and the kinetic energy of theopening discharge valve is accordingly quite great. The backing plateabsorbs or withstands this kinetic energy, and it is for this reasonthat the shape of the backing member is such as to conform to thenatural shape to which the discharge valve deflects upon opening, so asto avoid what would otherwise be high local stresses in the dischargevalve as it comes to a stop. The importance of the air cushion betweenthe discharge valve and the backing member will thus be apparent.

In FIG. 14, a modified form of the invention is' disclosed, in which theseparate valve seats 28 and 33 of FIGS. 1, 4 and 6 are replaced by asingle integral seat 53 having inlet openings 34' therethrough. However,instead of an annular discharge passageway, seat 53 has an annularseries of discharge openings 54 therethrough which are alternatelycovered and exposed by valve 45. Naturally, the lip 21 of piston 8 isomitted in this embodiment.

FIG. 15 shows a fragmentary cross section similar to the left end ofFIG. 1, but of a modified form of the invention in which the valves andtheir backing plates are reversed as to their radial order .and are of amodified construction. In FIG. 15, the inlet valve 55 is the radiallyouter of the inlet and discharge valves, and is backed up by a backingmember 56 suitably curved as was backing member 50 in the embodiment ofFIG. 1, for the purpose not only of minimizing wear on inlet valve 55but also of urging valve 55 against its seat. As best seen in FIG. 16,valve 55 is provided with three equally peripherally spaced notches 57.A dowel 58 is disposed in each notch 57, and backing member 56 has acurvature such as to press inlet valve 55 against its seat at thelocation of each of the three dowels 58. Inlet valve 55 thus flexes uponopening, into contact with backing member 56 between the dowels 58 butis held against movement relative to the dowels 58 by backing member 56at the location of the dowels 58 and hence does not rub against'dowels58 or undergo any other appreciable form of wear. Of course backingmember 56 also has correspondingly spaced notches (not shown).

Discharge valve 59 (FIG. 17) is similarly backed by a backing member 60by which it is held against its seat at the locations of three dowels 61disposed in three notches 62in the inner periphery of valve 59.

An advantage of the construction of FIGS. 15-17 is the simplicity ofproducing a notch rather than a tab.

It will be evident from a comparison of FIGS. 7l3, on the one hand, andFIGS. 16 and 17 on the other hand, that the number of tabs or notches,and in general the number of points at which the inlet and dischargevalves are secured to their seats against flexure, is variable. Ingeneral, the thinner the material of the valve, the greater will be thenumber of, points of securement; and the higher the operating speed ofthe compressor, the greater will be the inertia of the moving portionsof the valve and the thinner will be the valve material so as to reducethat inertia to a minimum.

From a consideration of the foregoing disclosure, therefore, it will beevident that all of the initially recited objects of the presentinvention have been achieved.

Although the present invention has been described and illustrated inconnection with preferred embodiments, it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit of the invention, as those skilled in this art will readilyunderstand. Thus, for. example, although each valve and each backingmember in the illustrated embodiments has been shown as being unitary,it is of course possible to subdivide these radially into a plurality ofconcentric valves and backing members between one common valve seat andone common valve retainer. These and other modifications and variationsare considered to be within the purview and scope of the presentinvention as defined by the appended claims.

valve seat at a plurality of regions spaced about the periphery of saidvalve and restraining the-valve from any motion relative to said valveseat at said regions, said valve being free to flex to an open positionbetween said regions, and means limiting the lift of said valve betweensaid regions.

2. A compressor as claimed in claim I, said one opening comprising acontinuous annular slot.

3. A compressor as claimed in claim 1, said opening comprising anannular series of spaced openings.

4. A compressor as claimed in claim 1, said valve comprising a flatannular wafer of thin sheet material.

5. A compressor as claimed in claim 1, said valve comprising a circularwafer of thin sheet material having a pair of arcuate slots that definebetween them a central securing region of said valve which isinterconnected with a peripheral region of the valve by a plurality ofperipherally spaced bridges of the material of the valve.

6. A compressor as claimed in claim 1, said valve having equally spacedprojections on a periphery thereof by which said regions are secured toa said valve seat.

7. A compressor as claimed in claim 1, said valve having projections ona periphery thereof by which said lift is limited.

8. A compressor as claimed in claim 1, there being two said regionsdiametrically opposed about the periphery of said valve, said valveflexing to an open position spins about an imaginary lineinterconnecting said regions.

9. A compressor as claimed in claim 1, which is a nonlubricatedcompressor.

10. A compressor as claimed in claim 1, said limiting means comprising abacking member having the curvature that is assumed by the openingvalve.

11. A compressor as claimed in claim 10, said backing member being anannular spring substantially more rigid than said valve.

12. A compressor as claimed in claim 1, said valve having equispacednotches in a periphery thereof, and dowels in said notches at saidregions of said valve.

13. A compressor as claimed in claim 12, said periphery being the outerperiphery thereof.

14. A compressor as claimed in claim 12, said periphery being the innerperiphery thereof.

1. A compressor comprising a cylinder, a piston reciprocable in thecylinder, means for reciprocating the piston, the cylindEr having inletand discharge openings communicating with the interior of the cylinder,annular valve seats concentric with said cylinder and bordering saidinlet and discharge openings, and valves for opening and closing saidopenings, each of said valves comprising an annular flexible valveconcentric with said cylinder and overlying one of said openings, meansmaintaining said annular valve against the adjacent valve seat at aplurality of regions spaced about the periphery of said valve andrestraining the valve from any motion relative to said valve seat atsaid regions, said valve being free to flex to an open position betweensaid regions, and means limiting the lift of said valve between saidregions.
 2. A compressor as claimed in claim 1, said one openingcomprising a continuous annular slot.
 3. A compressor as claimed inclaim 1, said opening comprising an annular series of spaced openings.4. A compressor as claimed in claim 1, said valve comprising a flatannular wafer of thin sheet material.
 5. A compressor as claimed inclaim 1, said valve comprising a circular wafer of thin sheet materialhaving a pair of arcuate slots that define between them a centralsecuring region of said valve which is interconnected with a peripheralregion of the valve by a plurality of peripherally spaced bridges of thematerial of the valve.
 6. A compressor as claimed in claim 1, said valvehaving equally spaced projections on a periphery thereof by which saidregions are secured to a said valve seat.
 7. A compressor as claimed inclaim 1, said valve having projections on a periphery thereof by whichsaid lift is limited.
 8. A compressor as claimed in claim 1, there beingtwo said regions diametrically opposed about the periphery of saidvalve, said valve flexing to an open position spins about an imaginaryline interconnecting said regions.
 9. A compressor as claimed in claim1, which is a nonlubricated compressor.
 10. A compressor as claimed inclaim 1, said limiting means comprising a backing member having thecurvature that is assumed by the opening valve.
 11. A compressor asclaimed in claim 10, said backing member being an annular springsubstantially more rigid than said valve.
 12. A compressor as claimed inclaim 1, said valve having equispaced notches in a periphery thereof,and dowels in said notches at said regions of said valve.
 13. Acompressor as claimed in claim 12, said periphery being the outerperiphery thereof.
 14. A compressor as claimed in claim 12, saidperiphery being the inner periphery thereof.